Can you create a shower on concrete slab?

We have a 1/2 bath downstairs and would like to add on and make it a full bath (shower and toilet - no tub). We live in a townhome that is on a concrete slab. Is it possible to add a shower to a 1/2 bath that's on a slab? Is it crazy expensive? Important to note, in order to expand the size of the small 1/2 bath, we will take a few feet from our garage space. The garage is one small step down from the floor level of the 1/2 bath, so we would have to build that area up. Thanks!